SPACI score report for 4b50 in ASTRAL 2.07:

PDB Entry: 4b50
SPACI score: 0.77
AEROSPACI score: 0.77

Experiment type: XRAY
Resolution: 1.3
R-factor: 0.1468
PCK1 PROCHECK Ramachandran: 1
PCK2 PROCHECK Chi-1 angle: 2
PCK3 PROCHECK H-bonds: 1
WCK1 WHAT_CHECK Packing: -0.702
WCK2 WHAT_CHECK Ramachandran: -1.147
WCK3 WHAT_CHECK Chi angles: -1.04
WCK4 WHAT_CHECK Backbone: 2.884

Note: Here are links to pages about PROCHECK and WHAT_CHECK.

Here is the full WHAT_CHECK report on this protein (linked from the WHAT_CHECK site).